Spacecraft require heat shields to protect components from atmospheric heating. Temperature measurements within the heat shield are useful during testing. To accomplish such temperature measurements it is desirable to mount thermocouples within the heat shield in blind holes.
Blind hole thermocouple plugs in carbon phenolic heat shields have inaccurately measured temperature due to cutting of the heat conductive fibres in the phenolic by the blind hole resulting in decreased heat flow across the hole. Also epoxy encapsulation of the thermocouple wire in the plug bottom groove has pyrolyzed at re-entry temperatures. The resultant low density char residuum retards heat flow to the thermocouple wire.